How Can Nevus Of The Tongue With Redness And Stiffness Be Treated?

My 95 year old father has a condition he says is called a nevus of the tongue. His was born with an enlarged tongue which looks purplish red
and he has difficulty sticking his tongue out. Recently he has complained of a stiffness of part of his tongue. This makes it difficult for him to eat soft food eg a moist fruit cake. He also dribbles. This condition does not last all the time but comes and goes. What could he do to releive this stiffness.