Si tens picor al braç, no has de tocar la ferida.

Si means if in Catalan, just like in English.

So:

• Si tens picor al braç = If you have itching/an itch in your arm
• si introduces the condition

Be careful not to confuse this with Spanish, where si also means if, but some other small grammar details differ.

Tens is you have (from tenir, to have).

Picor is a noun meaning itching, itchiness, or an itch.

So tens picor literally means you have itching or you have an itch.

Catalan often uses tenir + noun in places where English may prefer an adjective or a different structure.
For example:

• tenir gana = to be hungry (literally to have hunger)
• tenir set = to be thirsty (literally to have thirst)
• tenir picor = to have itching / an itch

Yes. That is very natural too.

• Si tens picor al braç = If you have itching in your arm
• Si et pica el braç = If your arm itches / If you feel an itch in your arm

The version with picor uses a noun.
The version with pica uses the verb picar.

Both are understandable and natural, though the exact feel may differ slightly depending on context.

Because a + el contracts to al in Catalan.

So:

• a + el braç → al braç

This is very common:

• al cotxe = to the car / in the car
• al carrer = to the street / on the street
• al braç = in/on the arm

So picor al braç means itching in the arm or an itch on the arm, depending on context.

Catalan often uses the definite article with body parts where English uses a possessive.

So instead of saying your arm, Catalan often says the arm, especially when it is already clear whose body part it is.

Here, because the subject is you:

• Si tens picor al braç naturally means If your arm itches / if you have an itch in your arm

This is very normal in Catalan:

• Em fa mal el cap = My head hurts (literally The head hurts to me)
• Renta’t les mans = Wash your hands (literally Wash yourself the hands)

Has de + infinitive means you have to + verb.

So:

• has de tocar = you have to touch
• no has de tocar = you must not touch / you shouldn’t touch

In many contexts, no haver de + infinitive expresses that something is not to be done, often like a rule, instruction, or recommendation.

Here:

• no has de tocar la ferida = you mustn’t touch the wound / you shouldn’t touch the wound

Depending on tone and situation, English may translate it as either mustn’t or shouldn’t.

No. The normal and correct form is:

• no has de tocar

Putting no before the infinitive like has de no tocar is not the usual choice here.

Catalan normally negates the whole verbal expression:

• No has de tocar la ferida = You must not touch the wound

So if you want to say don’t have to or must not, the exact interpretation depends on context, but the natural negative placement is before the conjugated verb: no has de...

Ferida means wound, injury, or sometimes sore, depending on context.

• la ferida = the wound

It comes from the noun ferida, related to the idea of being hurt or wounded.

Examples:

• La ferida fa mal. = The wound hurts.
• No toquis la ferida. = Don’t touch the wound.

Catalan often uses the definite article more than English does.

Here, la ferida means the wound, referring to a specific wound already understood from the situation.

In English, you might sometimes say don’t touch the wound or simply don’t touch it. Catalan naturally keeps the article:

• tocar la ferida = to touch the wound

Because Catalan often leaves out subject pronouns when they are already clear from the verb ending.

• tens already tells us the subject is tu (you)
• has de also tells us the subject is tu

So Catalan does not need to say tu unless it wants emphasis or contrast.

The full version would be:

• Si tu tens picor al braç, tu no has de tocar la ferida

But that sounds unnecessarily heavy in normal speech. The natural version is the one you were given.

Braç means arm.

The ç in Catalan is pronounced like s.

So braç sounds approximately like bras.

A helpful point for English speakers:

• c before a, o, u is usually a hard k sound
• but ç gives you the soft s sound

So braç is not pronounced with a k sound.

It is a very good and common word, especially for itching or itchiness as a sensation.

But depending on context, Catalan can express the idea in different ways:

• tenir picor = to have itching / to feel itchy
• picar = to itch
• coïssor can also appear in some contexts, often meaning stinging, burning, or a type of irritation

So picor is absolutely natural here, but it is not the only possible way to express the idea.

Yes. A very common alternative is the imperative:

• No toquis la ferida. = Don’t touch the wound.

That is a direct command.

By contrast:

• No has de tocar la ferida. sounds more like an instruction, rule, or recommendation: You shouldn’t / mustn’t touch the wound.

So both are correct, but the tone is slightly different.