I think i got bitten by a spider? how dangerous is a spider?

Usually not much: The vast majority of spider bites are from essentially harmless species that may cause a little local redness and swelling but nothing else. The two dangerous ones: 1) black widow found in woodpiles mostly (a rare problem) and 2) brown recluse found in basements and house corners. This one can cause a necrotic, enlarging wound which needs medical attention.