hi welcome to healthcare magic!
to upper arm could be due to acid reflux
,heart or may be local in nature.If your pain increases on excersising,is gripping in nature and is associated with sweating it is probable cardiac in nature and you may visit a cardiologist for an ecg and trop test
.However if it increases on applying local pressure to the area it may not be of cardiac origin.You may also try antacids to see if there is any decrease in your pain.If u find relief with these medications your pain is probably due to acid reflux and hence not a cause of worry.
Hope this helps!