welcome to hcm.
a swelling which is hard may be a bony one.
few questuions should be answered in cases of lump.
1.is it enlarging?
2.is it hard?
3.is it changing its size shape rapidly?
4.is there any associated systemic features like fever
if answers are YES then you should consult a surgeon.
the sweeling need examination and may be some investigations like FNAC.
I think you should have a consultation as it is large in couple of months and hard.
wish you a good health.