It would be great if you can mention the approximate size and the location where it is present
If it's around 1cm size, then nothing to worry about , can happen post infection, a course of antibiotics is often helpful.
But if more than 2cm or increasing in size with time, u need to get a USG neck and FNAC from the swelling done in that case
Health Tips
see for
1. rapid increase in size
2. any colour change
3. pus discharge
4. appearance of several nodes in neck or elsewhere
5. weight loss/ evening rise of temperature