My 2 yr old is stuffy with think green stuff, woke up today with hives, getting worse now, and has a dry cough when i laid him down for bed.

Needs to be seen: Please take him to the pediatrician, he needs to be examined and probably will need prescription medications, meanwhile if you can just irrigate his nose with saline , that would help the discharge and probably help the cough, as for the hives, not sure of your description, can be a rash related to an infection or an allergic reaction for whatever reason, wish you both wellness