Since your instrument is made of wood, its parts will expand or contract when it is exposed to changes in temperature or humidity. Try to protect your instrument from extreme changes in temperature, to avoid damage. Don't store it in an attic or a cold or damp basement. Don't leave your case near a heat register or radiator or in the sun. On the rare occasions when you are asked to perform outside, make sure you are shielded from the direct sun, and avoid playing outside when it is hot or cold. It's always a bad practice to leave your instrument in a car, but it's especially dangerous in hot or cold weather. Keep the humidifier in your case filled with water (if your case has this feature) or use a Dampit to protect your instrument from lack of humidity in winter.
Your instrument is glued together with a special type of violin maker's glue that is formulated to protect your instrument. If there is a lot of expansion or contraction of your instrument's parts, the glue will crack before the wooden parts of your instrument break. However, if a glued seam breaks open, your instrument can produce a buzz, or you may notice a loss of tone power. If you have either of these problems, you can check for an open seam by gently tapping a knuckle on the top or bottom of your instrument over the seams at the edges. An open seam will produce an obvious rapping sound. You can also visually inspect the instrument for gaps between wooden parts or flakes of glue around a seam. If you suspect you have an open seam, do not attempt to reglue the instrument yourself with ordinary household glue. Doing so may result in damage to your instrument, since this glue will not break under stress. Take your instrument to a violin shop, where they will clean out the old glue, apply some new violin maker's glue, and clamp the seam while the glue dries. This is an inexpensive repair. The shop will probably need to keep the instrument overnight. Do not delay in having an open seam repaired, because the open seam can create tensions in the wood of your instrument that may cause more serious problems, such as cracks in the wood.
On rare occasions, other problems may develop. For example, your instrument may develop a crack, a corner may be knocked off, an edge may be splintered, or your varnish may be scratched. A good violin shop can do expert repairs that will make such damage all but invisible.
A violin shop may do minor repairs on basses, such as regluing seams, but may be reluctant to take on more major repairs, because of the amount of room that a bass takes up in their shop. Basses needing anything more complicated should probably be taken to a luthier who specializes in basses. One bass luthier in the Washington area is listed at the end of this page. Your teacher may have some other suggestions.
Important: You should take your instrument to a qualified repair person as soon as you notice an open seam or a crack. If left untreated, these conditions can worsen, and a minor repair can become a major one.