A lot of it depends on what kind of surface you are landing on. If the "sometimes when you jump" part is landing on concrete, it's going to hurt (more than likely). Just kind of take it easy and practice landing from short heights, or just jumping up and down, to kind of "condition" your feet.
Shouldn't hurt at all if you're landing properly.
+1 Steve Low
Condition, condition, condition. Not just your legs, but your feet muscles, too.