Who to consult?

In my opinion this is not a legal issue at least not yet. Contact the company and give them an opportunity to correct the problem.

What legal action can I pursue?

Seek medical attention if needed. Absent injuries your damages are insufficient to warrant legal action.

I would like to sue McDonald's due to chemical burns. Is this possible?

You were injured in the course of your employment. Therefore I have re-posted your question to the workers compensation forum.

I agree with the prior answer. It is always better to get ahead of these issues rather than just ignore them and hope they'll go away.

Without injuries other than the gross out factor you have no damages and thus no claims.

How do I find out a doctor's malpractice claim insurance company name?

You should not be attempting this on your own. Discuss in detail with a local medical malpractice attorney instead.

How can I beat my chins case that came about from all false allegations

Your question is unclear. Please re-post with more details and context.

Case is closed in April 2016 and my pain has been getting worse now then it has before, would I be able to reopen it?

The entire concept of a Release is finality. Once the case is settled and the documents signed you cannot re-open.

My boyfriend found a piece of tooth in his rib tip dinner ?

Without damages other than the gross out factor he would have no basis for a lawsuit.

How can I reapply after denial of i-485?

Re-posting to the immigration form.