tiisana kega datta node, bansoukou wo itimai harimasita.

Both are possible.

• 小さな けが sounds a little more set-phrase-like and natural in many contexts.
• 小さい けが is also grammatically correct and means basically the same thing.

A useful thing to know is that 小さな and 大きな are special words that behave a bit like い-adjectives, but they can only come directly before a noun in this form:

• 小さな けが = a small injury
• 大きな 問題 = a big problem

You cannot usually use 小さな at the end of a sentence:

• natural: けがは 小さいです
• not natural: けがは 小さなです

So here, 小さな is just the noun-modifying form.

けが means injury, wound, or hurt from some physical accident.

It can refer to:

• a cut
• a scrape
• a bruise
• a small wound
• sometimes a more serious physical injury, depending on context

In this sentence, because it says 小さな けが, it clearly means a minor injury, such as a small cut or scrape.

Also, although けが can be written as 怪我, it is very often written in hiragana.

Because ので normally attaches to the plain form of what comes before it.

Here:

• けがだった = it was an injury / it was a wound
• けがだったので = because it was an injury

More specifically:

• けが is a noun
• when a noun comes before ので, it takes だ in plain style
• in the past, だ becomes だった

So:

• non-past: けがなので
• past: けがだったので

You may sometimes hear very polite forms like けがでしたので, especially in formal speech, but for standard grammar explanations, plain form + ので is the basic pattern.

Both can mean because, but they feel a little different.

• ので sounds softer, more explanatory, and a bit more neutral.
• から can sound more direct or more like the speaker’s personal reason.

So:

• 小さな けがだったので、絆創膏を一枚貼りました。 = Because it was a small injury, I put on a bandage.

  • calm, explanatory tone

• 小さな けがだったから、絆創膏を一枚貼りました。 = Because it was a small injury, I put on a bandage.

  • also natural, but a bit more straightforward

In this sentence, ので fits well because it sounds like a simple explanation of what happened.

Japanese often omits subjects and possessive words when they are obvious from context.

So this sentence does not explicitly say:

• I had a small injury
• I put a bandage on it
• my injury

But those ideas are understood from context.

A natural English translation needs to supply them, but Japanese usually does not.

This is very common in Japanese. If the speaker and situation are clear, leaving out the subject sounds normal and natural.

絆創膏 is read ばんそうこう.

It means:

• adhesive bandage
• Band-Aid
• plaster in some varieties of English

It is the small sticky bandage you put on a cut or scrape.

The kanji are fairly difficult, and many learners just memorize the word as ばんそうこう first. In everyday writing, people may also write it in kana as ばんそうこう.

一枚 is the counter for flat, thin objects.

A bandage is treated as a flat item, so:

• 絆創膏を 一枚 = one bandage

This is more natural and specific than 一つ.

Some common 枚 examples:

• 紙を一枚 = one sheet of paper
• 皿を一枚 = one plate
• チケットを一枚 = one ticket
• 絆創膏を一枚 = one bandage

You might hear 一つ in very casual speech when someone is not being precise, but 一枚 is the standard, natural counter here.

Because 絆創膏 is the direct object of the verb 貼りました.

The structure is:

• 絆創膏を 貼りました
• literally: applied/stuck a bandage

So を marks the thing that was put on.

Even though in English we often say put a bandage on it, Japanese focuses on the object being applied:

• 絆創膏を貼る = to stick/apply a bandage

貼る means to stick, to paste, or to apply something adhesive onto a surface.

A bandage is something sticky that you place onto the skin, so 貼る is the natural verb.

Examples:

• シールを貼る = put on / stick a sticker
• 切手を貼る = stick on a stamp
• 絆創膏を貼る = put on a bandage

In this sentence, 貼りました is the polite past form:

• dictionary form: 貼る
• polite non-past: 貼ります
• polite past: 貼りました

So it means put on / applied.

The sentence is describing something that already happened.

Past forms:

• だった = was
• 貼りました = put on / applied

So the sequence is:

1. there was a small injury
2. because of that, a bandage was applied

If you wanted to say it as a present or habitual kind of statement, the forms would change. But here it sounds like the speaker is reporting a completed event.

Yes. 一枚 explicitly means one bandage, so a very literal translation is:

• Because it was a small injury, I put on one bandage.

In natural English, though, we often just say:

• I put on a bandage
• I put a Band-Aid on it

because one is usually understood and does not always need to be stated in English.

So both ideas are present, but the Japanese is a bit more explicit about the number.

The comma is helpful, but it is not always strictly required.

It separates:

• the reason clause: 小さな けが だったので
• the main action: 絆創膏 を 一枚 貼りました

So it makes the sentence easier to read:

• Because it was a small injury, I put on a bandage.

In Japanese writing, commas are often used for clarity and rhythm. Whether one is included can depend on style, but here it is very natural.