Very true. One of the quickest ways to hinder consistency is developing pain. There are a few potential options:

Start by limiting your range of motion. Perform an exercise in a pain-free range, which is often a midpoint in the repetition. You want to eventually progress to a full range but partials can be a good integration.

Change the type of exercise. You may respond better to an open chain (leg extension and leg curl) or a closed chain (squats and lunges) for the upper leg.

Slowly building up your volume. On average, you only need 12 sets of exercise per muscle group per week. That could be two exercises for 3 sets twice a week. Many people over train in the early stages of training.

Change up the contraction type. Try bands, machines, free weights, and calisthenics. You may respond better to one over the other.

Focus on recovery. Ensure you are getting plenty of high quality sleep and high levels of protein.