I'm only guessing but is it possible that mark was the baby beginning to hatch? They sort of poke a circle of holes along the shell and bust outh. If there's anychance of this I would just leave the egg be and let the baby hatch, sometimes it can take days. I wouldn't say all hope is lost.
Remember that even if the hatching doesn't succeed, that you did your best with the resources you had and you at least provided the dove a chance to hatch. If you'd left it on the pavement it surely would have been eaten or stepped on. I understand your sadness and am hoping for the best, but the fact that you made the effort to save it at all is something to be proud of.