Other day i got iv sodium chloride drip for dehydration and needle went into soft tissue muscle, made my arm flex and hurt a bit. it was resolved and went down but i worry. could i still possibly get complications from this?

Unlikely. You should be OK now that it has gone down and resolved. Make sure to drink enough water and get electrolytes in order to avoid future dehydration. Avoid alcohol and caffeine until your dehydration is all better.

Usually not. Maybe a bruise/. In the old days we used to give saline this way when you could not find a vein in patient and we still do it in cats and dogs,