Even if it's foregone that you have cylinder head or valve damage, it's hard to be sure how big of a job repairing it might be without some sense of whether it's a problem in one or more cylinders.
Time for a compression test. Depending on the sound, it might be valve lashing / tappet noise, or, a sign of damage (and more damage being done). I wouldn't run that engine until you know which, or you could just make things worse, for example, you may be generating metal fragments that are scouring grooves in the cylinder sleeves and will require an a cylinder sleeve overbore and new pistons (on top of the cylinder head replacement or repair).
Good luck