What chemical dissolves propellant?
The main issue is to prevent as much scaring as possible. As previously recommended in this thread keep the wound clean and covered with Neosporin or the like. By decreasing the scaring the foreign material will work its way out. If the material is into the deep dermis and subcuetaneous tissue you have a tatoo and no solvent will remove it with out creating scaring in that tissue plane which will cause you to loose some function of your hand. In this case less is definitely better than more.
All the best,
Prosecute criminals to the fullest extent of the law and their weapons will become harmless.
"Let us speak courteously, deal fairly, and keep ourselves armed and ready." Theodore Roosevelt 1903