Si te cortas el dedo, lávatelo bien antes de ponerte una tirita.

Because after si for a real, possible situation in the present or future, Spanish normally uses the present indicative, not the subjunctive.

So:

• Si te cortas el dedo... = If you cut your finger...

This is the standard pattern:

• Si + present indicative, + command / future / present

For example:

• Si llueve, no salgas.
• Si tienes hambre, come algo.

You would not normally say si te cortes here.

Here te means yourself. The verb cortarse is being used reflexively, so te cortas el dedo literally works like you cut yourself on the finger or you cut your finger.

In Spanish, this is very common with body-related actions:

• Me lavé las manos = I washed my hands
• Se rompió la pierna = He/She broke his/her leg
• Te cortas el dedo = You cut your finger

So te shows that the action happens to you.

With body parts, Spanish often uses the definite article (el, la, los, las) instead of a possessive like my, your, his, especially when the owner is already clear from a reflexive pronoun.

So Spanish prefers:

• te cortas el dedo
• me duele la cabeza
• se lava las manos

rather than:

• te cortas tu dedo
• me duele mi cabeza
• se lava sus manos

In English, your finger sounds natural. In Spanish, el dedo is more natural here because te already tells us whose finger it is.

Because with a positive command, object pronouns are attached to the end of the verb.

So:

• lava = wash
• te = yourself
• lo = it

Together:

• lava + te + lo → lávatelo

This is very common in Spanish imperatives:

• Dímelo = Tell it to me
• Póntelo = Put it on
• Llévatelo = Take it away / take it with you

In contrast, with negative commands, the pronouns go before the verb:

• No te lo laves

In lávatelo:

• te = yourself / for yourself
• lo = it

Here lo refers to el dedo.

So the structure is basically:

• Lava el dedo
• Lávatelo = Wash it well

The te is there because the action is being done to your own body.

The accent mark is there to keep the original stress of the command lava when the pronouns are added.

Without pronouns:

• lava → stress naturally falls on la

When Spanish attaches pronouns:

• lava + te + lo → lavatelo

Now the word is longer, so the natural stress pattern would change. To keep the stress in the right place, Spanish adds the written accent:

• lávatelo

This often happens with commands plus attached pronouns:

• pon → póntelo
• lava → lávatelo
• dime → dímelo

Because after a preposition like de, Spanish uses the infinitive, and any pronouns usually attach to that infinitive.

So:

• antes de ponerte una tirita = before putting a plaster on yourself / before you put on a plaster

Not:

• antes de te poner

This is the normal pattern:

• antes de acostarte
• después de lavarte las manos
• sin decirme nada

Pronouns can attach to an infinitive, just as they can attach to a positive command.

Literally, it is to put a plaster on yourself.

The verb poner means to put, and ponerse often means to put something on oneself.

So:

• poner una tirita = to put on a plaster
• ponerte una tirita = to put a plaster on yourself

In natural English, we would usually just say put a plaster on it or put on a Band-Aid.

In Spain, una tirita means a sticking plaster / adhesive bandage / Band-Aid.

It is a very common everyday word in Spain.

Depending on the country, other terms may be used, such as:

• curita in many parts of Latin America
• Band-Aid in some contexts, especially informally

But for Spanish from Spain, tirita is a very natural choice.

Here bien means something like well, properly, or thoroughly.

So:

• lávatelo bien = wash it well
• more naturally: clean it properly / wash it thoroughly

In this sentence, bien emphasizes that you should clean the cut carefully before putting on the plaster.

Yes. Lávatelo is the affirmative informal command for tú.

The basic tú command of most verbs is formed from the él/ella/usted present form:

• lavar → lava
• comer → come
• abrir → abre

Then pronouns are attached:

• lava → lávatelo

If the speaker were talking to usted, it would be:

• Láveselo bien antes de ponerse una tirita.

That sounds more formal.

Yes, that would also be very natural.

There is a slight difference in focus:

• Si te cortas el dedo... = If you cut your finger...
• Si te haces un corte en el dedo... = If you get a cut on your finger / if you make a cut on your finger

The original sentence focuses on the action of cutting yourself. The alternative focuses more on the resulting cut. Both are common and natural.

Because Spanish uses pronouns very often with:

• reflexive verbs
• body parts
• commands
• infinitives

In this one sentence, you get several common patterns:

• te cortas → reflexive
• el dedo → body part with article
• lávatelo → command + attached pronouns
• ponerte → infinitive + attached pronoun

So although it may look dense at first, it is actually made up of very common Spanish structures. This is the kind of sentence that helps learners see how natural Spanish handles everyday actions involving the body.