Immune complex symp
You don't say what you reacted to, but there is an infection called parvovirus
b19 in which, after the person is over the infection, the immune complex response causes arthralgias that can last up to 2 years.
They always eventually resolve. If your reaction was to a medication, you should get better, but recheck with your doctor if worried. A new illness may overlap with your prior one and confuse.