I had a UTI and was on nitrofurantoin for a week. I just finished the treatment, yet my groin still hurts when I pee and my urine is dark. Normal?

No! Although Nitrofurantoin is notoriously ineffective to treat many uti's, especially if prior antibiotic exposure has selected out resistant GI bugs that cause most uti's, your symptoms reflect a potential complicating issue of urologic stone disease that could be obstructing and can give groin pain when in the lower ureter. You need a spiral ct to exclude a ureteral stone with a repeat urine eval.!