Hi there, Last week, I noticed a small, pea sized lump just underneath my mastoid process on my left side. It's not painful and it can't be moved. Also around the same time, a rash on my scalp appeared, also on my left side and I've been having some sinus issues...phlegm in throat, stuffed nose, sinus pressure. Could all of these things (the rash, the sinus issues) be related to the lump? Is it something I should be worried about? Thanks!