if it were me i would try and remove the fish from its mouth. this happened to me with a spotted perch and an otocinclus but the oto was so far in that it wouldnt come out due to the spines on its pectoral fins. the perch couldnt swim properly due to the extra weight in its mouth and both died. i tried for ages to free them but it just wasnt happening
A wet towel to hold the oscar, a pair of needle nose pliers to remove the victim. Try to wiggle the RTBS as you pull it out. Mine did the same thing with a bristlenose plec.