It usually goes away within a few hours.

But be careful! Always use precautions. Use a bit of cologne or here's a good one: buy like several high quality incense with the high quality oils, then just leave them out in your room and when them have no more smell burn them and buy some more.

The reason why I say take precautions is because some weed may not be real stinky until you burn it then it gets real smelly. This happened to me once in high school and I walked into class and the whole classroom smelled it quickly and I got sent to the nurses office to "get deskunked".

Oh and brush your teeth and don't forget about your hair.