Is it bad that blood got out after injecting an insulin needle

Generally no: Drop of blood may be from hitting a capillary but continued bleeding is likely from hitting a vein or artery. Injecting into a vein or artery can cause sudden drop of sugar leading to dizziness, nausea, sweating, blacking out - if you feel these then take some sweet juice or candy and make sure someone knows what you may have done - or call doctors/ems.