Hard lump behind my left ear. Should I be worried?

Question

I noticed it around 6 weeks ago, a hard lump behind my left ear. It doesn't move and doesn't really hurt if i touch it. I asked my husband to look and he said it doesn't look like a pimple.  I dismissed it and thought it would go away . However, I've noticed its still there and slightly increased in size. Am I being overly cautious booking doctors? has anyone had this issue before?

Thanks!