What Causes A Lump In The Calf Muscle?

Hi! I was putting lotion on my legs last night and found a hard lump about the size of a dime on the inside of my left calf muscle. The skin is slightly red at the site. It is not painful. I do not remember injuring my leg at all. My brother has had blood clots in his leg, though, so I am wondering if this is something serious or not. Thanks for your help!