Problem with concrete post and front gate!

[Niaz]

Last weekend I took off our olld rotting front gate (approx 900 x 900) and replaced with one from home base which was the same size although the horizontal two bars were in a different position (slightly narrower).

Due to this I had to drill 2 new holes in the concrete post both we and our neighbour share for gate fixings at the front of our mid-terrace houses. I drilled 2 new holes at the base in the required position, as was planning on using the existing holes and rawl plugs that were already in the post as they matched with the type of hinges i was using. However when i came to screw the first screw through the hinge and into conc. post, a chunk of it blew off the side of the post. Now i'm stuck on how to fix to the post, i can't move it more centrally as neightbours latch is in place, i can't move up as post and adjacent wall return with rebates so can'y do that. I also cannot move down past blown area as gate witll be dragging across floor - any suggestions!!!!