Yes, the red light will work for both congestion and pain. Let the light shine on any affected area for 1 to 2 minutes. If you have a lot of area to cover, like I do, consider buying two lights to cut the time in half.
The next day, the congestion should be much better. The light breaks up proteins and makes the cells more energetic, so they are pumping stuff out and assimilating stuff much faster. More ATP, or cellular energy, is being generated. I think it also creates new lymph channels, but I cannot be sure about that. Current research is just catching up to the market place, so you may be able to learn more by going to another vendor's web page for red light therapy and reading up. I just like this unit because it is totally portable (no wires) and reasonable in price.
Let your body rest a day before new treatment. Since I have lymphedema, and my lymph nodes are not there to pump lymph, I have to do this every other day. It is like washing dishes, the work is never done for me. But since you are "whole and functioning" I think you may get relief in only a few treatments.
It certainly does not cost too much to find out. The only ongoing expense is AA batteries. I recycle those.