Muscle pain and swelling?

The other day while walking I started getting these sharp pains around my ankle. I stopped and rotated my ankle, thinking it was a cramp or something but it didn't help. Since then it's been reoccurring, some days not as bad as others but it's still there. It mostly occurs when I am walking down or up flights of stairs or on inclines or declines. Sometimes if I've been on my feet it hurts when walking on a flat surface. It hurts right on the top of my ankle, where the tongue of your sneakers reaches, and also on the inside of my ankle. I noticed yesterday that there is a bulge (im guessing swelling) on the inside of my foot directly above my ankle bone and extending about three inches. I can prod the area and it hurts but it isn't stiff. The area on the top of my foot also hurts to the touch but there isn't any obvious signs of swelling or anything like there is on the inside of my ankle. I was thinking it may be something with my muscles as I can rotate my ankle fine without it hurting. It only occurs when I am walking up or downwards. It's a sharp, burning pain, sometimes lasts several seconds after I step. Just looking for some suggestions.