Barnet håller handen mot kinden när det gör ont i örat.

Because barnet is the definite form, meaning the child, while barn means a child / child.

Swedish usually adds the definite article as an ending:

• barn = a child
• barnet = the child

So Barnet håller handen ... means The child is holding ...

Håller is the present tense of hålla, which often means to hold, keep, or place and keep.

Here it means something like:

• holds
• keeps

So Barnet håller handen mot kinden is literally The child holds/keeps the hand against the cheek.

It sounds natural in Swedish for describing a physical position.

Swedish often uses the definite form of body parts where English would use a possessive.

So Swedish prefers:

• Barnet håller handen mot kinden
  rather than
• Barnet håller sin hand mot sin kind

This is very common with body parts and clothing when the owner is already obvious from the context.

Using sin hand is possible, but it sounds more emphatic or contrastive, as if you want to stress that it is the child’s own hand.

For the same reason as handen. With body parts, Swedish often uses the definite noun instead of a possessive.

So:

• mot kinden = literally against the cheek

Even though English would usually say against his/her cheek, Swedish does not need the possessive here because it is already clear whose cheek it is.

They are definite because Swedish commonly uses the definite form for specific body parts in a situation like this.

The sentence is talking about:

• the hand
• the cheek
• the ear

not just any hand, cheek, or ear.

Also notice the definite endings:

• hand → handen
• kind → kinden
• öra → örat

The ending depends on the gender and type of noun.

Mot means against or toward, and it fits the idea of pressing or holding something in contact with something else.

So:

• mot kinden = against the cheek

If you said på kinden, that would mean on the cheek, which is possible in some contexts, but mot is better here because it suggests contact/pressure, which fits the gesture of someone reacting to ear pain.

Here när means when.

It introduces a subordinate clause:

• när det gör ont i örat = when it hurts in the ear / when the ear hurts

So the whole sentence describes what the child does when this pain happens.

Here det is a dummy subject, similar to English it in it hurts.

It does not refer to a specific thing. It is just part of a very common Swedish expression:

• det gör ont = it hurts
• literally: it does/makes hurt

So in när det gör ont i örat, det is not standing for the child or the ear. It is just the normal grammatical subject in this expression.

Göra ont is a fixed expression meaning to hurt or to be painful.

Examples:

• Det gör ont. = It hurts.
• Det gör ont i benet. = My leg hurts / It hurts in the leg.

Literally, gör means does/makes, but you should learn göra ont as a whole expression rather than translating each word separately.

I örat literally means in the ear.

Swedish often uses i when talking about pain located in a body part:

• det gör ont i örat = the ear hurts
• literally: it hurts in the ear

This is very natural Swedish.

Because the sentence is talking about one ear: the ear.

Forms:

• ett öra = an ear
• örat = the ear
• öron = ears
• öronen = the ears

So:

• i örat = in the ear
• i öronen = in the ears

If both ears hurt, Swedish would normally use the plural.

Because när starts a subordinate clause, and Swedish keeps normal subject-verb order inside that clause:

• det = subject
• gör = verb

So:

• när det gör ont i örat

This is different from main-clause word order in Swedish, where the verb often comes second.

For example:

• Det gör ont i örat. = main clause
• ... när det gör ont i örat. = subordinate clause

In both cases here, det gör stays together in that order.

You could, but it would sound heavy and unnatural in ordinary Swedish.

Swedish usually avoids repeated possessives with body parts when the owner is obvious. That is why the original sentence sounds much more natural:

• Barnet håller handen mot kinden när det gör ont i örat.

Using:

• sin hand
• sin kind
• sitt öra

would sound overly explicit unless you are making a contrast, such as:

• inte hennes hand, utan sin hand
• not her hand, but his/her own hand

Yes. Swedish noun gender affects the indefinite article and the definite ending.

In this sentence:

• ett barn → barnet
• en hand → handen
• en kind → kinden
• ett öra → örat

So:

• common gender nouns often take -en in the definite singular
• neuter nouns often take -et in the definite singular

That is why you see both -en and -et endings in the sentence.