I'd go with arm/shoulder, as already suggested. Or leg; a bolt to the leg doesn't have to pin somebody to make it very difficult to move around. If the victim is sensitive to the sight of their own blood, that could be used to your advantage.
A few notes on bolt size: modern bolts (or quarrels) are NOT the same as medieval era bolts. Not in materials, thickness, length, fletching, tip design, or anything else, really. Modern fiberglass (and other materials) are typically longer than medieval equivalents, which were made of wood (like ash) and had to be short and heavy or they'd blow apart upon firing. On the flip side, there are modern bolts that are much smaller than medieval equivalents, particularly (but not limited to) those fired from one-handed crossbows.
I'm not sure from your posts what era this is taking place in; modern bolt lengths are very easy to come by, so you can look them up. But medieval lengths are harder to find. You'll need to decide what kind of crossbow is being fired and from what era, then find the length of bolt for it. They range from short (8 inches and smaller) to long (15+ inches) to very long (for ballistae and such). It is completely plausible to pin a victim with either a medieval or modern bolt, but certain styles (fired from matching styles of crossbows) will be much more plausible than other styles.
Exactly what behavior to expect when the bolt hits a body is dependent on the crossbow and bolt designs. Heavy medieval war crossbows could easily sport 200lbs or more of draw force and used bolts with wicked tips. Against an unarmored person, such a bolt would usually rip right through unless it struck a bone, in which case it wouldn't stick out of the body. That means no pinning unless the victim had armor or light cover to slow the bolt down a bit. Lighter medieval field crossbows would have lighter draws and be more likely to pin a victim, but less likely to penetrate armor. Hunting bolts were different from war bolts, and modern practice bolts are different from modern hunting bolts. Outside of some very specialized organizations, there are no modern war bolts.
The exact behavior will be different for each. Depending on your audience and how factual you want to represent things, you may need to consider the bolt's behavior on striking its target and not just where it struck.
