I Met With An Accident And My Knee Got Injured

i met with an accident and my knee got injured and had severe body pain also.dr prescribed me phexin,dolomax etc.i took the medicine for 3 days.when i ate that my stomach was feeling very bad.my stomach was having a burning sensation.so i stopped taking phexin..even though i stopped that burning sensation is not going.should i consult a dr? why is this happens?