Can I sue after I underwent painful surgery to remove cyst/tumor caused by drug lithium administered to me for panic attacks?

The most difficult question I see is that of causation. To prevail at a trial (which is part of the calculus of reaching a settlement), you'd have to have an expert witness to testify that (a) prescribing Li was outside the applicable standard of care; and (b) that ingesting Li was the direct, proximate, foreseeable, natural (any combination of these adjectives) cause of your injury. There is more that must be shown. Your doctor's opinion is of interest, but it usually is not enough: you need an expert who has reviewed the literature on the subject. You can find a lawyer who is versed in the rather specialised area of products liability on the web (try Avvo.com), in the yellow pages, from the Lawyer Referral Service at your State Bar. Also most major personal injury law firms handle products liability cases. Since the incident occurred about 19 months ago, I think you should consult such a lawyer as soon as possible, in order to avoid missing any applicable limitations periods.