Thanks for asking the query,
Your clinical history suggest that you had developed a sweeling at the injected side of your arm which you are feeling as haematoma
If you are comfortable with your day to day activities it is advisable to apply a bandage at the side, so that the haematoma resolves faster.
If the skin over the haematoma is showing any signs of unhealthiness, its better to consult a physician and get the checkup done.
Follow the post operative instructions given by the Dentist
Maintain a good oral hygiene
Hope this helps out.