Warmth, cuddly stuffed animal, mirror, feather duster (?) ... What's wrong with it's foot? Where are you located?
You could use a regular 60 watt light bulb for warmth, depending where you live & ambient temps. Chicks need about 95* for the first week or so, decreasing 5* weekly. You'll know if they're cold, lots of chirping. You could also try a heating pad (MHP by Blooie). I've used a feather duster (mimic a hen) but others discourage it stating the chick(s) can get tangle/strangled with it ... A cuddly fuzzy stuffed animal works too, remove anything (strings, buttons, decorations, etc...) that it could get into trouble with. Mirror so it can see it's self, thinking theirs another chick ... I keep a radio on with soft music so it thinks it's not alone.
Depending how old it is when you introduce more chicks, you'll probably have to do a slow introduction. Best wishes