I agree with others, he needs to go to the vet, looks like MBD. Do you use calcium on his food and a
UVB light? In the mean time get the sand out and put him on paper towel or newpaper, if the sand gets in it, it could get infected and become worse.
Possibly this is all due to the sand and his mouth and eye got infected from it being dirty?
Either way I would suggest a vet.