The 'self-extracting' bolt is there to help remove the crank. It needs to go back in. Thread the bolt back into the axle and then insert and tighten fully the retaining ring, possibly a left hand thread. Finally you can undo the bolt, which will push against the retaining ring to gently push the crank off.
There's a really good (imo) video by Park Tool here if you like that sort of thing