I would not worry so much about cheating the workout, but what's going on in that knee.
Knees are a delicate affair (same goes for shoulders btw.). We need them for a lifetime.
Lots of tendons, cartilage and other stuff that is easily offended. Muscles grow at a nice rate, but the rest of the framework has to adapt to that. You opened up a dialog with your knee: You're telling it: WORK and the answer was: OK, but only so far!
When you are young it's easy to ignore it, but the older we become, the more we should listen to that.
Take it easy. It's not a sprint, it's not even a marathon. It's a looong walk.
Better listen to your body and march for a while. If it does not go away, maybe let a doctor have a look at it.
All the best.