I am a 33 healthy woman. my left foot back has been sowllen for 4 days and feel a little bit painful when i strech it. the color of the skin is normal

Heel cord issues?: This sounds like it might be achilles tendinitis, bursitis, among other things. If ice, stretching, and over-the-counter antiinflammatories do not help, see a podiatrist or orthopedist.

"back of the foot : Pain could be achilles tendonitis, a haglunds deformity or posterior heel spur. Try wearing a clog type shoe or backless shoe to avoid pressure. I wold have x-rays taken to help differentiate the above possible causes. Ice, antiinflammatories and sometimes immobilization may be helpful.