I noticed a lump growing under my skin is this dangerous?

For the past 3 days I have had a splitting migraine that has been making me sick to my stomach. Today I noticed a lump growing under the skin on my temple (right side) on a vein. What could it be? Is it potentially dangerous? It itches but it is NOT a bug bite. Yes I have an appointment but its not until friday (this friday) so even though its 2 days off I am concerned. I have not bumped my head or been hit there or anything like that so please help me figure out what it could be. It is skin colored but very hard.