MK is absolutely right. No one can tell for sure what a lump is unless it is taken out. They can have a good idea based on some indicators, but stick around here long enough and you'll find a lot of people whose doctors were wrong. Not trying to scare you, because as MK said 80% of all lumps are benign, but you are right to question. Get it out and get certainty.
Best of luck,
Do not go gentle into that goodnight,
Rage, rage against the dying of the light.