Jason Banton's first-half solo strike had put the visitors in front but Harry Pell equalised almost immediately to level matters.
Sheridan said: "We deserved a point. I thought we started really well and deservedly went in front but it's so disappointing to have let them back into the game so quickly.
"That's just a lapse in concentration and it's gives them a lift to come back fighting for the three points and is something we could have avoided.
"Since I have been here we have been good at holding on to leads so it's disappointing that it had to come to an end in this game.
"Both teams knew what was at stake, all the teams around as at the bottom are fighting hard and putting together some good results so it was a bit nervy but that's to be expected."