You absolutely can be allergic to metal! In fact, nickel allergy is one of the most common forms of allergy in the world. Typically a nickel allergy will show up after a few days of wearing jewelry with nickel in it, although if you have previously been sensitized to the nickel, the allergy may show up more quickly.
Nickel allergy causes of a type of allergic reaction known as contact dermatitis. Contact dermatitis causes redness, itching and, sometimes, blistering of the skin. Treatment of contact dermatitis includes, obviously, refraining from wearing the jewelry that was causing the problem. Additionally, most of the time, it is necessary to apply a topical steroid cream to reduce the redness and itching and encourage healing.
Your primary care doctor
can confirm the diagnosis of contact dermatitis. They can also prescribe the steroid cream that you will need to get the symptoms under the control.
In the future, you can avoid further flares of the allergy by avoiding all jewelry that contains nickel. In particular, pure silver jewelry should be safe and should not cause any problems.
Go see your primary care doctor to confirm the diagnosis and to get treatment under way as soon as possible!