Anytime a kitchen smells like something infinitely more gross than food, it is never a good thing. If you have sniffed around and found that your smelly smell is emanating from your dishwasher, you have a problem.
While it is true your dishwasher tub might need a solid cleaning, in truth the interior usually stays pretty clean. After all, the act of washing your dishes usually cleans the tub pretty well too. However, your dishwasher can grow smelly not because it needs to be wiped down, but because it has food still lingering inside.
Every dishwasher is built with a food trap in the bottom of the appliance. This food trap catches the larger particles of food, and occasionally a loose small dish, to prevent them from going down the drain. This food trap is necessary to prevent eventual clogs in the appliance or drain line. Unfortunately, as the food builds up, it causes some pretty nasty smells.
To empty the food trap in most dishwasher models, you will likely need to remove the bottom spray arm. This will typically snap in and out. Once removed, you can lift up the cover below and uncover the food trap. If your dishwasher has been notably slow draining recently, this can be the cause as well. If the food builds up in the trap thick enough, obviously it will have trouble draining water through it. So you are not only solving the smell issues but an actual dishwasher problem as well.
After throwing away the food, you may also want to flush the food trap out in the sink to remove the smaller particles before placing it into the appliance. You can then add the cover back on and install the spray arm. After another wash, the smell should subside fully. However, you can also run a cycle using vinegar as a detergent to help dissipate the smell immediately.