The military is a massive organization, and unless you have a enlistment bonus or reenlistment bonus in writing, it never happened. There are many stories of recruiters or retention officials making promises of bonuses for signing on the dotted line.
A burning sensation is a particular type of pain distinct from dull, stabbing, or aching pains. A burning kind of pain is often related to nerves, but there are many other potential causes. Injuries, natural wear and tear, infections, and autoimmune disorders all have the potential to cause nerve damage and pain.
But take a breath. There are many things that can cause muscle twitching, including fatigue, anxiety, or even a pinched nerve in the spine. Muscle cramps, too, are very common, and can be caused by such things as over-exertion or even dehydration.