26 days post thighplasty, still wearing compression, drains in, noticed lump (Photo)

This is a collection of fluid which can be recurrent for many weeks. One solution is to have a drain for continuous drainage. 

Hi, 
26-days post-op is a very long time. In my practice (as well as in the practice of almost any surgeon) leaving drains for more than 12-14 days is not considered to be safe. Even if the drains become full, we generally discard the negative pressure after 3-5 days and let the drains only do suction to the excessive fluid, not with suction pressure. In every case (even if the drains are full) we remove the drains at most on7-10th day and leave the patient with moderate compression garment. Keeping the drains for so long time increases the occurance of pseudo-cyst and continuous discharge as well as increasing the risk of drain-site infections.
The comments above may not applicable to you and these are only the general principles that we follow. You should consult your PS for the medical advices.
Best wishes,

Congratulations on your thigh lift, nicolboiseau!
Your drains may be clogged, which is why popping that small lump may have triggered more drainage. Don’t worry because there’s no harm done.  
However, 26 days is quite a long time to still have drains. I suggest that you go for a follow-up consult with your reputable and board-certified plastic surgeon so that you can have your drains monitored.
Good luck!