Solitary bee means only that it doesn't form colonies, of course. You may find lots of solitary bees in one place. People are encouraged to make structures which look like a whole lot of drinking straws viewed end on, just to help solitary bees have nest sites in one place.
Solitary bees won't swarm; they're solitary; and have no hive to protect. That's one less reason for a solitary bee to sting, but none of our bees are aggressive if undisturbed. You can get stung by the humble bumble bee, but that won't happen unless you lie on one (as I did as a child) or put it in a similar situation where it is driven to sting you .