A had a strange dream a few nights ago. 
I was driving down a road, apparently icy, and saw two large vans in front of me slipping and sliding.  I slowed down and managed to avoid an accident but the two vans collided.  When I got out of my car, a guy who showed up out of nowhere tells me to stick around because I may need to take the injured to a hospital.  Then he asks if I know first aid.  Two nuns in blue and yellow habits show up out of nowhere and say that they can help with first aid.  Then I woke up.

Interpretation:

Witnessing an accident is a warning to be careful for the next few days or you may be injured, though probably not the same way as in the dream

To dream of a hospital indicates illness, but I didn't actually see one, just heard someone say it

To dream of an unknown man indicate a favorable event

To see a nun in a dream is a sign of hope, and blue is also a good omen

So my overall interpretation:
I need to be careful for the next few days to avoid an injury and, if I do, it will probably lead to something favorable.