Your gum must have got irritated due to following reasons.
1. Poor oral hygiene. Tats you could have got calculus
and stains that has formed a band impinginging tat s pressing on your gums to cause inflammation and bleeding.
2. Any improperly fitting partial or complete dentures
3. Acrylic or plastic fixed partial dentures that are being improperly maintained.
4.Deficiency of Vitamin C and B complex
For al the above mentioned facts commonly you should undergo scaling and then remove the other causative factors. Please consume lemon mosambi, Amla vit c rich foods to nourish your gums. Visit your dentist