How To Cure Pain In Achilles Tendon Of Left Foot?

I noticed my left foot near my Achilles tendon/heel started hurting. I did not do any thing to my knowledge that would injure it and no other part of my foot is hurting. When I wake up it does not hurt even when I walk around. However, when I wear my shoes throughout the day it starts to hurt and toward the end of the day it hurt a decent amount more than the beginning of the day. When I take off my shoe and press where it hurts when I have my shoe on, I cannot feel any pain. It only seems to hurt when I have my shoes on and am walking. I'm not sure what is wrong. It is only that one foot.