Thanks for writing to HCM
Firstly you need X-ray of Tibia
in AP/Lateral view. It can exclude many probable causes.
since it is hard in consistency, swelling may be bony in origin.
You didn't mentioned your age. There are many causes of swelling depending upon age and sex.
You need proper clinical examination and investigations.
Besides X-rays, you need routine hemogram,RBS.
Since history is short, it may be infective in etiology.
Treatment depends upon clinical examination and investigation reports.
You should consult orthopedician.
Get well soon.