Pain after lunges and Squats?

Hello, i'm 21 and I've haven't worked out ever since high school. I'm trying to get in shape, so I had an appointment with a personal trainer on thursday. I was fine afterwards, with no pain except for pressure on my knees and legs. The next day I woke up with awful pain!!!! My knees buckle when I walk, and sitting down or going up the stairs is really painful. Today is Saturday, and I'm still in pain. My backside feels a lot better, but the front of my thighs are still killing me. I expected soreness, but this feels awful! Is this something I should worry about?