Sorry to hear this, Megglevache, you must be horribly worried.
I've no personal experience, but my gut reaction would be to take him straight to the GP - they'll be able to allay fears or refer as necessary (and then with a proper diagnosis you'll be in a better position to decide whether an osteopath might be good in conjunction/instead).
My experiences with HVs is that they'll only tell you to go to the GP anyway, so best to go straight there, imo.