Hi I Have What Seems To Be A Swollen And

Hi I have what seems to be a swollen and tender part of my skull bone on the posterior right occipital bone junction. I have been to my docs today and he says it does not feel like a cyst nor is it a swollen lymph node? He's not sure what it is but he seems to think that it is some sort of 'infection' just beneath the scalp and has given me Flucloxacillin 500mb tabs to take 4 times a day. There was no previous occasion where this part of my skull has been this sore before, I only noticed it a day ago when I was drying my hair with a towel when I rubbed over it and felt the pain then compared it to the left hand side bone to feel that it was quite tender and swollen in comparison. Any further ideas or suggestions please ?