Wecome to HCM
if for TB it is seen after 48 hours and swelling redness
is expecte it is induration of more than 10 mm is significant as you say there was no induration.
This redness is due to hypersesitivty to PPD( TB Antigen) it will subside with some more time.
Usually no treatment is required for this.
You can just do a Ice fomentation.
Hope this will help you.