help!! milk supply drop, need tips

i’ve been breastfeeding my baby for 10 months now, he had a fall and bit his tongue quite bad 2 nights ago, went to a&e and they said he’d be fine and sent us on our way.. but he wasn’t feeding. so 24 hours go by and he’s still refusing breast other than a few sips from his sippy cup (straw, doesn’t use his tongue much), so we was debating to go and take him back to hospital, he was upset already so i thought what’s the worst that could happen and tried to offer him boob again, and he had it. but the problem is, he left me engorged for 26 hours with no milk leaving, so now he’s eating again it takes a lot longer and i don’t think he’s getting as much as he use to. his feeds before use to be 6-8 minutes long on one breast, now they go on for 40-60 minutes with both breasts, but he ends up still sucking but they’re empty so i have to take him off.

any tips on how i can quickly increase my milk supply again?