Hot water issue in master

About two months ago we lost most of the hot water in the master bathtub. All other bath/faucets have hot water. It worked fine up until we replaced the hot water heater, then about two weeks later, the hot was was greatly decreased. It is a single lever, Price-Pfister. When you turn the lever all the way to the hot, very little hot water comes out. Maybe 25% of normal. Is it possible there could be debris in the pipe? If so, could I dis-assemble the valve and briefly turn the water back on? Would this blow out any debris that might be in the line? Any other suggestions? Thanks.