Hi. Welcome to HEALTHCARE MAGIC.. As per your complain it seems that your lower labial frenulum is inflamed leading to redness and swelling.. It can occur due to injury with any hard or sharp foods, toothbrush trauma, burning with something hot or due to chemicals injury or burning like concentrated solutions of mouthwash.. You should apply numbing gel containing Lignocaine over it.. Take anti-inflammatory painkillers like Ibuprofen.. Apply cool compresses or such ice and do cool water rinses.. Take soft and bland foods.. You can cool your food to room temperature before eating.. If still does not improve consult an Oral hygiene and get evaluated.. Hope this helps.. Regards..