Vacuum pressure exerted & isolated on the end of your penis can produce some fluid retention on the underside of your penis in the frenulum area.
It is not detrimental to weight hanging or pumping. Over time as your penis becomes more conditioned to the stress and work load it will diminish.
Edema is easily displaced if after your hang session or pump session, you use some Tender tape to wrap the area. A snug compression wrap of the area for 15-20 minutes will get rid of it. Wrap snug, but not tight enough to inhibit circulation.
Installing a Girth Band over the wrap is helpful too.