Never lower the weight unless you are unable to do a full rep on that weight with good form.
Its called DOMS, it will go in a few days just stretch or use a foam roller, rest the muscles for a few days and increase your protein intake the help them repair. Use heat rub or get a sports massage if it's really bad. I often struggle to get up and down stairs the day after a leg sesh, just gotta suck it up.
Lol! This is so ironic because I was doing my leg workout 2 days ago, and did similar exercises with the same weights. I've been sore as hell to, but give it time and it will go away.
You should try Romanian Deadlifts for your hamstrings, it works wonders.