Folic acid (folate) is a complex B vitamin. Along with vitamin B12, folic acid is required for the formation of normal red blood cells and for the synthesis of DNA (deoxyribonucleic acid), the genetic material of cells. Folic acid is also necessary for the normal development of the fetal nervous system.
Pregnant women or women of childbearing age should take folic acid supplements to reduce the risk of having a baby with a birth defect, especially neural tube defects. The folate serves to ensure a healthy pregnancy and good development of the baby. If a pregnant woman has folic acid deficiency, there is an increased risk of having a baby with a congenital spinal cord or brain defect (neural tube defect).
If you really can't move your arm because of the sting, and there is pus, the best thing you can do to yourself is go to the Emergency doctor. You can take an ibuprofen if the pain is too hard.