Ay, I haven't personally experienced that after tetanus shot, but a few of us moms in my group did complain ng muscle soreness and achiness for a day or two after, parang normal vaccine reaction lang talaga. Since you're saying it's severe though, I'd really suggest checking with your doc or even calling your midwife/clinic to describe exactly how bad it is and where, kasi they'll know best if it's just the usual post-vaccine soreness or something else na kailangan i-monitor. Paracetamol or ibuprofen usually helps with the general achiness, pero with severe pain it's better to get it checked out to be safe, yun lang!