I Ddon't Wwant Being Nto be negative

For titles, we don't usually capitalize the first letter of every single word! Usually just the first word and other important ones

I pinched myself my skin of my little finger with an iron bar.

Pinch is usually a small injury. Do you mean more serious ones?

I Don't Want Beingto Be Negative

“Being” does not work here

I pinched myself mythe skin of my littlepinky finger with an iron bar.

1. “Myself” and “My skin” ultimately mean the same thing, except one is more specific, so it sounds weird to say both
2. “Little finger” works, but in English we call our smallest finger the “pinky” :)

I don’t think it'’s not verythat serious, but I'm still in the emergency room because I may need some stitches.

This sounds more natural

I Don't Want BeingTo Be Negative

Yesterday was a difficult day,. I went to the gym and I had a little accident.

I pinched myself myaccidentally pinched the skin ofn my little finger with an iron bar.

I don't think it's not very serious, but I'm still inwent to the emergency room because I may need some stitches.

I Don't Want BeingTo Be Negative

Yesterday was a difficult day, I went to the gym and I had a little accident.

Just a heads up, "I had a (little) accident" has a double meaning of wetting yourself. You can use "had a little incident" or "had a small injury" to avoid that

I pinched myself mythe skin of my little finger with an iron bar.

I think it's not very serious, but I'm still in the emergency room because I may need some stitches.

You mean you went to the emergency room yesterday and you're still there? That's a very scary waiting time.

I Don't Want Beingto Be Negative

"I don't want to be negative" is a more natural way to say it. Uses the imperative form of the verb 'to be'.

Yesterday was a difficult day,. I went to the gym and I had a little accident.

Use a period for a complete thought.

or

Here, since you already said 'yesterday', for past-tense, you could also use a connecter for cause and effect: because.
For example: "Yesterday was a difficult day because I had a little accident at the gym."
This is more natural.

I pinched myself mythe skin of my little finger with an iron bar.

"I pinched myself on the finger with an iron bar." also works.

Your finger belongs to you, so you do not need to repeat the pronouns myself/my.

I don't think it's not very serious, but I'm still in the emergency room because I may need some stitches.

More natural.