lumps on forearm?

hi guys i’m 18F, 136 lbs, 4’11 and relatively healthy besides having arrhythmia (PVC). i noticed a palpable, painless lump on my left distal forearm mid-late october with no recall of any injury to the area. i had an ultrasound done where they said there was no masses or abscess in the area, however i went to an oncologist for a second opinion. she said that because the swelling is relatively mild that it won’t be targetable for a biopsy. i’m going back for a repeat ultrasound on the 22 of december. i’m just worried for malignancy because everytime i search it up, i’m told that it’s cancer. it’s painless (even with deep palpation), squishy, there’s nothing that’s “grabbable” (thus, i can’t move it). i also don’t have any symptoms like persistent fever, unexpected weight loss, or excessive fatigue. anyone have any idea what it could be? i’ll try to attach a video in the comments if anyone is curious what it looks like.