Can be painful. Can be painful, but not that dangerous.
Depends on species. Many species of tarantulas are not harmful to humans. If a tarantula bites it might be a “dry” bite – injecting little to no venom. However, the bite of some tarantulas can cause pain & swelling at the site, muscle cramping, fever, difficulty breathing and exhaustion. The chinese bird spider (a type of tarantula) has been blamed for one death in china.