Generally for dna contaminated with pcr inhibitors I would use phenol chloroform extraction but you might first try running a pcr with increased (double) the amount of magnesium ( many inhibitors remove Mg from the reaction mix) and secondly use less dna. Less dna means less inhibitor so often works better. Try a titration of DNA amounts compared with your usual amount...1/2, 1/4, 1/8 and 1/16 and 35 cycles of pcr. Some pcr enzymes are designed to cope with pcr inhibitors so any enzyme recommended for amplification from, for example, whole blood will probably work better than the commonly used taq polymerases