itami ni taemasita.

It is read:

いたみ に たえました。
Itami ni taemashita.

A more natural written form in Japanese would usually be:

痛みに耐えました。

Japanese normally does not use spaces between words.

The dictionary form is 耐える (たえる).

So:

• 耐える = to endure, to withstand, to bear
• 耐えました = endured / withstood / bore

耐えました is the polite past form.

This is a very common question, because in English we often think of pain as the direct object: endure the pain.

But in Japanese, 耐える often takes に:

• 痛みに耐える = to endure pain
• 困難に耐える = to endure hardship
• 暑さに耐える = to withstand heat

So with 耐える, the thing being endured is commonly marked by に, not を.

You can think of it as:

• to hold out against pain
• to withstand pain

That is why 痛みに耐えました is natural.

Usually, learners should stick with 痛みに耐える.

痛みを耐える is generally not the standard form taught for this verb. The safest and most natural choice is:

• 痛みに耐えました

So if you are learning the pattern, remember it as:

• N に 耐える

耐える has the nuance of bearing something difficult without giving in.

It often sounds like:

• enduring something painful
• withstanding pressure
• surviving hardship
• putting up with suffering

So 痛みに耐えました does not just mean pain existed; it suggests someone kept going despite it.

Both can relate to enduring, but the nuance is different.

耐える

More like:

• to endure
• to withstand
• to bear something severe

It can sound more serious, and is often used for pain, stress, pressure, hardship, weather, etc.

Example:

• 痛みに耐える = endure pain

我慢する

More like:

• to put up with
• to hold back
• to refrain
• to tolerate

It is very common in everyday speech and can also mean resisting the urge to do something.

Examples:

• 痛みを我慢する = put up with the pain
• 甘いものを我慢する = resist sweets / refrain from eating sweets

So for physical or severe suffering, 耐える can sound stronger or more formal than 我慢する.

It means the enduring happened in the past.

So the sentence says that the person did endure it.

Depending on context, it may imply:

• they managed to bear the pain
• they got through it
• they endured it for some period of time

Because Japanese often leaves context unstated, the exact time frame depends on the situation.

The sentence does not explicitly say.

Japanese often omits the subject when it is clear from context. So this could mean:

• I endured the pain
• he endured the pain
• she endured the pain
• they endured the pain

You need context to know who the subject is.

If you wanted to state it clearly, you could say:

• 私は痛みに耐えました。 = I endured the pain.
• 彼は痛みに耐えました。 = He endured the pain.

Yes. 耐えました is polite.

Compare:

• 痛みに耐えました。 = polite
• 痛みに耐えた。 = plain/casual

You would use 耐えました in polite conversation, writing, or when speaking respectfully.

Because 痛み is a noun, while 痛い is an adjective.

• 痛み = pain
• 痛い = painful / hurts

This sentence needs a noun before に耐える, so 痛み is the correct form:

• 痛みに耐える = endure pain

You would not normally say 痛いに耐える.

No. It is used for many kinds of things that are hard to bear or withstand.

Examples:

• 暑さに耐える = withstand the heat
• 寒さに耐える = endure the cold
• 圧力に耐える = withstand pressure
• 困難に耐える = endure hardship
• 孤独に耐える = endure loneliness

So 痛みに耐えました is one example of a broader pattern.

Yes, it is grammatically natural.

However, by itself it can sound a little context-dependent, because Japanese often expects the listener to already know:

• who did it
• when it happened
• what situation this was in

So it is a perfectly good sentence, but in real life it often appears with surrounding context, such as:

• 手術の間、痛みに耐えました。
  During the operation, I endured the pain.

• 彼は最後まで痛みに耐えました。
  He endured the pain until the end.