Can’t get 10g septum in from 12g. no pain, just stuck

Been at 12g for a quite few months now, no pain at all. Trying to go to 10g with internally threaded jewelry, but it won’t go in at all even the tip. Could it be the shape? Can’t afford a taper/pincher. Im sure its healed enough just cant seem to get the first bit in without it slipping. Any advice?