Nilipokata kucha vibaya, kidole changu kilianza kuvimba jioni.

It is built into the verb. In Swahili, subject pronouns are often attached to the verb instead of being separate words.

• ni- = I
• so nilipokata already includes the idea I cut / when I cut

That means you usually do not need a separate word like mimi unless you want emphasis.

It can be broken down like this:

• ni- = I
• -li- = past tense
• -po- = when / at the time that
• -kata = cut

So nilipokata means roughly when I cut or when I was cutting in this context.

This is a very common Swahili pattern: a lot of grammar gets packed into one verb word.

In this sentence, -po- is giving a time relationship: when.

So:

• nilikata = I cut
• nilipokata = when I cut

It connects the first part of the sentence to the second part. English usually uses a separate word like when, but Swahili can build that meaning inside the verb.

Its most direct meaning here is when I cut. In real translation, though, English may sometimes use after I cut or once I cut, depending on context.

In this sentence, the idea is:

• first, the nail was cut badly
• later, the finger started swelling in the evening

So when I cut my nail badly is the literal structure, but the overall sense can feel close to after I cut my nail badly.

It can be either, depending on context.

Kucha is one of those nouns whose singular and plural often look the same. So it can mean:

• a nail / fingernail / toenail
• nails

In this sentence, the broader context suggests one specific nail was cut badly, even though kucha itself does not clearly force singular in the way English does.

Swahili often leaves out the possessive with body parts when the owner is already obvious from context.

So nilipokata kucha vibaya can naturally be understood as when I cut my nail badly.

If you want to make it explicit, you could say:

• kucha yangu = my nail
• kucha zangu = my nails

But in normal speech, leaving that out is very common if the meaning is already clear.

Here vibaya means badly, wrongly, or in a bad way.

So kukata kucha vibaya means something like:

• cutting a nail badly
• cutting it the wrong way
• cutting it too short / injuring yourself while cutting it

As for the form, vibaya comes from the adjective idea bad, but in Swahili some forms like vizuri and vibaya are commonly used adverbially:

• vizuri = well
• vibaya = badly

So even though it begins with vi-, here it is functioning like an adverb in English.

Not always. Kidole can mean finger or toe.

If you want to be specific, Swahili can say:

• kidole cha mkono = finger
• kidole cha mguu = toe

In this sentence, the natural interpretation is finger, because of the context of cutting a nail and then having it swell.

This is noun class agreement.

Kidole belongs to noun class 7 in the singular, and class 7 uses agreement forms like:

• ki- on verbs
• cha- with possessives

So:

• kidole changu = my finger
• ki-lianza = it started (with it agreeing with kidole)

That is why the verb is kilianza, not alianza or ilianza.

For comparison, the plural is:

• vidole vyangu vilianza = my fingers started

In Swahili, possessives usually come after the noun.

So:

• kidole changu = my finger
• literally, something like finger my

This is normal Swahili word order. English puts the possessive first, but Swahili usually puts it after the noun.

Because kuanza means to begin / to start, and it is followed by another verb in the infinitive.

So:

• kilianza = it started
• kuvimba = to swell

Together:

• kilianza kuvimba = it started to swell

This is very similar to English started to swell.

If you wanted to say simply it swelled, without the idea of starting, you could use a different form, such as kilivimba.

Jioni means in the evening or that evening.

Swahili often does not need a preposition like in with common time expressions. So you can just say:

• jioni = in the evening
• asubuhi = in the morning
• usiku = at night

So kidole changu kilianza kuvimba jioni means my finger started swelling in the evening.

Because Swahili does not have articles like English a, an, and the.

Whether something is understood as:

• a finger
• the finger
• my finger

depends on context, possession, and other markers.

So kidole changu already clearly means my finger, and Swahili does not need a separate word for the.