I got a sunburn on my forehead and now I have a bump that looks like I got hit in the head with a baseball what is this?

Forehead lump. This swelling, which is not blistering, is unusual after a sunburn, but it appears to be a collection of fluid(edema) and may be akin to Sun poisoning. Apply cool compresses to see if the edema recedes. See your physician if not improved.