Congrats on your weight loss! It encourages me, as I'm trying to lose 40 lbs. in 3 months. I used to train female body builders (before I got old and fat) and the rule our trainer always used was "no pain - period." If it hurts, it's damaging your muscles. He always told us to work up to the point of pain and no further.
I know the "no pain, no gain" philosophy is what most people go by, but it's not a good one. If your legs start burning, stop and walk until they don't hurt anymore. If they don't stop burning, go home and rest.
What causes irreversible soft tissue damage is to continue to stress the tissue once it is already telling you to stop. I trained a lot of ladies, and you know what? They had fewer injuries than the other group and their injuries healed faster because they did not push themselves when they were already hurting.
Do what you want, but just think about it. If your child told you his leg hurt, would you force him to keep running? Treat yourself just as well.