NEED HELP!

Up until last night everything was ok electricaly with my car. Then my (-) Battery terminal came loose and of course everything shut off after i turned the car off. when i connected everything, i would step on the brake and the dash lights would come on, release the brake and they would turn off. i don’t really understand why this would happen? i checked the fuses and there all fine. has anyone had this happen to them b4?

the pos and neg post must have touched frying a relay or circuit in your u may have to re wire your brake and your dash lights to fix it

rewire? not looking forward to doing that. i hope its just a relay