While some people have reactions to the vaccine, the incidence is very low. There are reports of rashes and/or pain at the injection site, muscle pain, malaise and other complaints that may or may not be related. You don't state the age of your son or if this was his first vaccine or a booster. Check in with your doctor.
Reactions to the tetanus toxoid vaccine can include localized pain at injection site, headache,and tiredness. Babies can sometimes cry for long periods afterwards and could have a fever.
Common side affects include redness, swelling, and a bump or rash on the area of the shot. Moderate effects include fever and mild to severe pain in the area. In rare cases, severe symptoms such as anaphylactic shock and death may occur.
You should expect pain, redness and swelling at the site of the injection. He may also have an achy arm. Other reactions should be discussed with your doctor.