The symptoms that you describe do sound like puppy strangles, although it is very difficult to tell without examining him. The last case I saw though had very similar signs, especially with the facial itching too. The best way to be sure is to have your vet take a small needle aspirate of the lymph node and get it examined - strangles should come back as a sterile lymphadenopathy ie the lymph nodes are reactive but not due to an infection. If this is the case then steroids are needed, but a cortisone injection by itself is not enough - they need low doses orally by mouth daily for 1 week and then every other day. However, in such a young dog, it is important to have the diagnosis before using steroids - so get the lymph nodes checked first. If this isn't the cause, then the lymph node aspirate should give a much better idea of what is going on.