Hi. Thanks for your question. I am a board certified neurologist in the U.S.
Yes, there is a chance that this warm feeling you are experiencing could be related to a nerve impingement coming from the lumbar spine. In particular, injury or pressure on the L2, L3, or L4 nerve roots could conceivably cause such a feeling. However, another area that could potentially be involved is a nerve called the lateral femoral cutaneous nerve which runs down the outer area of the thigh to supply sensation to this region. Patients who are overweight or wear tight fitting clothing around the waist are at risk of developing this condition. In this situation, there is no easy fix, but wearing looser fitting clothing and/or losing weight can be helpful to relieve the problem.
In either condition, if the problem is persisting, there are various medications which help for nerve pain that can relieve the discomfort. Of course, if there is a pinched nerve in the low back, sometimes other treatments can be tried such as physical therapy, antiinflammatories, and even surgery to relieve the pressure on the nerve.