Was cleaning the outside bin earlier(been away so had moldy food waste and flies in)now i have bad stomach pains and feel sick.should i be concerned?

Yes and No: You could be sick from exposure but the onset of illness is very fast. You may have already had the infection brewing and symptoms are unrelated to the refuse bin. Either way if the pain gets worse, you start to vomit or get diarrhea, or you get dehydrated get help.

Stomach pain: You may have inhaled mold spores or other vile particles. You may have absorbed mold spores onto your tongue and swallowed some. It is reasonable to associate your current sickness with the exposures to mold and fly excrement. What to do? Sip plenty of fluid, slowly. Ice cold is better than hot. Eat minimally right now. Pepto Bismol (bismuth subsalicylate) or Alka Seltzer may help. Is safe to try, I believe.

Symptoms suggestive: You may be experiencing symptoms of mold toxicity due to exposure to mycotoxins (toxins produced by molds). If your symptoms persist, see your physician who can examine you, do diagnostic laboratory testing, and provide treatment, if necessary.