Hi there - it's me again !
There are a few things that could cause this. A physical injury, an allergy to plants which their ears touch when they're grazing, a badly placed ear tag which is irritating or infected and so on.
It's difficult to say without seeing photos or (better) actually feeling the ear but the fact that it's crusty and spreading makes it sound a bit like mange and you need to sort that out quickly otherwise it will spread even more. Have a look on the 'net for Demodectic Mange which tends to cause the skin to go lumpy as the mange is inside irritating the flesh.
You'll find an iodine based treatment for it easily in France (Betadene for example) without having to fork out for vet's prices but you may also need an antibiotic. Anyway, check first what the problem is and have a look at the options. If you need any more info, post in the forum again.
Irene