Can drug-induced lupus cause long-term damage before it's cured?

Not likely. If the disease/lupus has not caused problem, it should not cause long-term trouble because removing the offending drug will often be the cure of this type of lupus. If it is has been an on-going for years before diagnosis, it is quite possible permanent damage to organs such as kindey/heart/lungs/brain. If not, likely u are ok after stopping the culprit. Consult doc. Good luck.
Sometimes. It depends on the location. Stopping the offending drug can usually stop the process. The long term damage can be limited but an acute process can cause damage that can last with scarring and thus continued symptoms.