HELP found a sick pigeon

i found a sick pigeon today huddled on the sidewalk under a ledge (it had been raining). it wasn't wet though, but the feathers look all mangy and dirty and i was able to just walk up to it and cup my hands around it and bring it inside. i don't want to leave it outside, and am afraid to take it to a vet since i have heard that since it is "just a pigeon" they will euthanize it and that seems sad. is there anything i can do to try to help it get better?

it seems able to walk fine, but cannot or is unwilling to fly. the wings however do not appear broken or damaged. it's feathers are all fluffed out and it has just been sitting, not moving, looking very depressed. like i said, the feathers look mangy.

can you help? or would it be better to take it back outside and let nature take its course? that seems sad but i don't want to prolong its suffering.