naknak: pus
pagnanaknak: severe formation of pus, suppuration
magnanaknak: will swell, will form pus on it, will suppurate
Suppuration is the process of pus forming.
A less severe formation of pus is revered to in Tagalog as nana.
In simple terms, you can think of nana as a light formation of watery pus, while naknak is serious heavy pus.