In my opinion it could be due to medical condition called Costochondritis.It is an inflammation of the cartilage that joins the ribs to the chest bone. It is this inflammation that causes the sharp chest pains inside the chest wall
As your cardiac tests are ok, so nothing much to worry. Take painkillers.
Hope you will be fine
Does the pain get settles by taking painkillers?
Which medications have you taken?
Feeling of tightness , can be considered as similar to get a pain.
So i would say that taking Painkillers will helps you .As you have not investigations done and no other cause is found, so possible diagnose seems to be- Costochondritis.