Last night the different dorms on our campus played sand volleyball against eachother, so I was in the sand barefoot for about 2 hours. After a while, my feet started to hurt so I thought "no big deal, it will go away." Anyway, this morning I woke up and they hurt when I walked around, so I looked at them and it looks like there are grains of sand shoved under my skin or something. I know it's not athlete's foot because I've had that before (that was awful, make sure you never play really physical sports without using good clean socks). What could it be/how do I get it fixed?