something similar happened to me too because I used a crap screwdriver. A watch smith could remove it with a proper one, otherwise he said he would have had to drill it
I assume this is from a threaded lug bar? if so, as pointed out, use a straightened out paper clip or for something that's more solid or a 2mm drill bit to push it out. try to drip the lug area with wd-40 to lubricate or loosen it