M.M.
This happens to me from time to time, after a particularly good workout.
It could be anything, but I've never had it be a concern.
I mentioned it to my chirporactor. He said that the effect of various muscles around the sinus cavities, in addition to the heating of the muscles (particularly the traps) and cavities can cause changes in pressure in there. Thus, temporarily stopped up ears or noses (or the opposite, should you be sick, for example).
Once the body cools back down and things return to normal, it will clear up.