If you happen to eat some bad ground beef you may experience vomiting, stomach pain, diarrhea etc.
Usually you'll recover just fine in a day or so if you do get sick from eating the bad ground beef but if not you should see a doctor.
If you just took one bite of bad ground beef and only swallowed just a bite of the ground beef then you might not even get sick or get sick as bad as you would if you ate a whole hamburger from the bad ground beef.
If the ground beef is bad enough you will likely start vomiting within 5 to 10 minutes of eating the ground beef.
Usually you can tell when ground beef is spoiled as it will usually have a terrible smell to it or have a slimy feeling to it.
If it smelled okay and tasted okay and was properly kept frozen before cooking it then it shouldn't be bad but if the ground beef smells bad or has a bad taste to it or is slimy then throw it out.