Asthma attack and coughing in the er last night.home today and i have a backache across my upper back?

Asthma: This is common and related to the excessive coughing and accessory muscles you were using during the asthma attack to try to get oxygen into your tight lungs. It will resolve although you could try a heating pad or acetaminophen. I would not recommend nsaids (advil, aleve (naproxen) aspirin, Ibuprofen or motrin) since those can sometimes trigger or worsen breathing in the rare individual with asthma.

Most likely it is : Muscular in nature which means it should get better with some time with heat and massage being helpful. If it persists or worsens, then see your physician.