Gout maybe?
How long has this been going on? Any injury prior to this? Rolled ankle, step funny, fall... You start a running regimen for your workouts? Increase intensity of work outs?
Could be 1 of a million things. Simple like shim splints from over use to stress fractures to heart disease. If it's been ongoing for a while and you have tried the rest, ice .... routine it's time to go see a doc. Google may be a helpful for a lot of things, medical advise isn't one of them.