My 19 mo. Old has small lump on right side of neck, hard but slippery. Healthy, bit of allergies, had a bug bite close to that area a few days ago.

Likely reactive. Lymphadenopathy or a lymph node that is swelling in response to the bite. As long as it remains small, less than an inch and is mobile and starts to resolve with time, it will be fine. If not, let your doctor take a look. All the best.