Hi, i fell with mountain bike on shoulder. very painful but manageable. in sling as painful if moved. should i see a docter? or give couple of days?

See doc : The sooner you see the doc, the better, as it will shorten recovery, specifically if shoulder dislocated and/or fractured. Start with GP if having one.

Hard to predict: Question of boney injury but could also be localized bruising. Perhaps biggest issue is rotator cuff tear. Over next few days, if you are losing mobility, having more pain, time to see doctor and perhaps engage in therapy.