Soft lump on front of pastern- windgall?

I have a 7 yr. old TB cross gelding who has developed a small, squishy lump (smaller than a quarter) about 1.5-2 inches above the coronet line on the front of the pastern --below the fetlock on his right front leg. It is not warm, and he shows no signs of pain or tenderness. He is completely sound and had a 3-week vacation from his usual dressage workouts -- which is about 45 mins a day, 5 days a week-- (I was traveling) over the holidays. I noticed this lump a week or so after I returned and began riding and don't know how long it's been there.

Our vet did an ultrasound and confirmed fluid build up from the joints. He mentioned that it's an odd place to have such liquid- since he normally sees it closer to the fetlock joint. He suggested infiltration in three sites to remove the liquid. I am new to horses and looked up this condition - which may be a windgall? We live in Costa Rica, so this term was not used, but other than the location- which is below the fetlock- on the front of the pastern- it looks to be windgall or windpuff.

I'm hesitant to proceed with infiltration without a second opinion. I've read that the fluid only returns after the procedure. The vet did an ultrasound on the left front leg and saw minimal fluid there as well, though there is no visible lump. He recommended infiltration on both to be extra sure, but I am worried about such an invasive procedure. Does anyone have experience with fluid build-up in this area? Most say that windgalls (if that is what this is) are non-threatening and rarely cause lameness. Just to leave it as it and regular exercise may help it.

Any suggestions/advice appreciated!