You can sometimes avoid the need for an injection by pinching the eyelid so that it bruises slightly and puffs up - just enough to stop the eyelid turning in again. (All the injection does is swell the lower lid to do exactly the same thing, using either a saline solution or, if there's already some infection, an antibiotic solution.)
If the cornea is already scratched then some soothing cream will help him feel more comfortable. Orbenin is the one usually recommended for entropion, but if you want to give him something soothing before the shops open on Monday, then I guess any eye ointment would help - Optrix, Bob Martin's, whatever you've got!
There are also some things called Michel clips to hold the eyelid open, but I have only heard about them (they are mentioned in some of the Eblex literature too), never seen any nor know where to buy them.