yubi ga itai node, kyou ha piano wo hikimasen.

It is read:

ゆび が いたい ので、きょう は ピアノ を ひきません。

A few useful notes:

• 指 = ゆび
• 痛い = いたい
• 今日 = きょう
• 弾きません comes from 弾く, which is read ひく when it means to play a stringed instrument or keyboard instrument such as the piano

Yes, but Japanese expresses this idea differently.

痛い is an i-adjective, and it means painful / sore / hurts.

So 指が痛い is literally something like:

• My finger is painful
• or more naturally in English, My finger hurts

Japanese often uses an adjective where English uses a verb.

Because 痛い is not a verb that takes a direct object with を.

In 指が痛い, the particle が marks the thing that is experiencing the state of pain:

• 指が痛い = The finger hurts / My finger hurts

Using を here would be ungrammatical.

が is the normal choice when saying what hurts.

• 指が痛い = My finger hurts

If you said 指は痛い, it would sound more contrastive, like:

• As for my finger, it hurts
• My finger hurts, though...

So が is the more natural default here.

Because Japanese often leaves out information that is obvious from context.

If someone says 指が痛い, it is normally understood as my finger hurts, not someone else’s finger.

So:

• 私の指が痛い is possible
• but 指が痛い sounds more natural in many situations

This is very common with body parts in Japanese.

ので means because, since, or so.

In this sentence:

• 指が痛いので = because my finger hurts

It gives the reason for what comes next:

• 今日はピアノを弾きません = I won’t play the piano today

So the full idea is:

• Because my finger hurts, I won’t play the piano today

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

• から is more direct and conversational
• ので is often softer, calmer, and a little more explanatory

So:

• 指が痛いから、今日はピアノを弾きません。
• 指が痛いので、今日はピアノを弾きません。

Both are correct, but ので sounds slightly more polite or less blunt.

Here は marks 今日 as the topic or frame:

• 今日は = as for today / today

This gives the sentence a time frame:

• Today, I won’t play the piano

Without は, 今日 could still appear, but 今日は is very natural when setting up what is true for today in particular.

It can also imply contrast, such as:

• Today I won’t play it
  maybe on another day I will

Because ピアノ is the direct object of 弾きません.

• ピアノを弾く = to play the piano

So を marks the thing being played.

Also, remember that the particle を is pronounced o.

弾きません is the polite negative non-past form of 弾く.

The Japanese non-past can refer to:

• the present
• the future
• habitual actions

Here, because the sentence includes 今日, it naturally means the future for today’s situation:

• I won’t play the piano today

So although the form is technically non-past, the context makes it future in English.

Because Japanese often omits the subject when it is obvious.

In this sentence, the speaker is talking about:

• my finger
• my decision not to play piano today

So I is understood automatically.

A more explicit version would be possible, but it usually sounds less natural unless you need emphasis.

It can mean either, depending on context.

Japanese often does not mark singular vs. plural clearly unless it matters.

So 指が痛い could mean:

• My finger hurts
• My fingers hurt

In many beginner translations, it is often rendered as my finger hurts, but the Japanese itself does not force that exact number.

Good question. 弾く originally has a sense related to plucking or striking strings, and in modern Japanese it is the standard verb used for playing instruments such as:

• ピアノを弾く = play the piano
• ギターを弾く = play the guitar
• バイオリンを弾く = play the violin

So even though the English verb is just play, Japanese uses 弾く for these instruments.

No, it is not strictly necessary, but it is very common.

The comma helps show the pause between:

• the reason: 指が痛いので
• the main statement: 今日はピアノを弾きません

So it makes the sentence easier to read, especially in writing.