We are not doctors. I have no medical training at all. Any medical advice or theories that I present you with will be pulled from a website. Or personal experience, which is honestly quite limited. For example, I could tell you that I have a sore throat at the moment and it feels like there is a lump in my throat when I swallow (true btw). This, however, is not the same as your situation.
In short, look it up on the web. If you can't find anything, call the NHS helpline. If they can't help or what you find on the web is not helpful or positive, tell your friend to book a doctors appointment.
Because seriously, for all we know it could be throat cancer or a chest infection or thrush or leprosy or simply a sore throat.
Doctors are there for a reason.