accidentally crossed positive and negative with a ratchet wen putting battery back on I have power to lights but car will not start. it wont even try to start I'm thinking fuse or relay does anyone have any ideas as to what it could be

thanks in advance

 

Any of a number of things could have shorted out or tripped. Check the main maxi fuses first, then the ones for the PCM, both located in the engine compartment by the battery. I think they're 60 amps at the bottom row of one of the two fuse boxes (upper and lower). I believe the one for the BCM is in the fuse panel on the end of the dash on the driver's side.
Could have shorted out the battery too.

 

ditto to plumbob, esp on zapping the battery