I've bruised my coxix. is there anything i can do to help it heal faster?

A bruise on/in a bone indicates that trauma caused disruption of the blood vessels which resulted in leaking of blood or localized bleeding. It is painful and takes a week or more to heal. There is nothing you can take to help heal it faster, but the discomfort can be reduced by taking Acetaminophen. Try not to take Ibuprofen, Naproxen or other NSAIDS as they can encourage more bleeding.

Avoid re-irritation. Perhaps us a donut pillow or other cut-out so no pressure on area when sitting. Time to heal and avoiding aggravation is most helpful.