if it keeps growing throughout the next few days, chances are it's an infected lymph node. My coworker just had a bacterial infection in a lymph node, started out as pea sized lump on back of neck and grew over next few days until it was as big as a chicken egg. She waited too long to go to a doc, so it had to be lanced. Went away with antibiotics.
That's just an idea of what it COULD be, but since you posted 2 weeks ago the problem should already been resolved i hope.
Anything CAN be cancer, and you can't know for sure without getting it checked, but to be honest, I have found pea sized lumps on the bottom of my hairline several times throughout my life. They ended up going away on their own. Now, if it doesn't go away, then get it checked.