I felt like i had those lumps too this summer, but when i discussed it with my CDE she said it was nothing and ok. I study medicine so i guess i am just becoming a hypochondriac from time to time
I use arms and abdomen for novolog, as the novolog should absorb fast and i have fastest absorption there. I use everything waist down (butt, thighs, calves) for tresiba. the thing with a basal insulin is, it doesn't have to absorb fast, as it is a long acting insulin. that's the whole point of it.
So i would definitely go back and try gluteus etc. with the pump you pumped both basal and bolus at the same place so fast absorption was crucial, here you have the luxury of using slower absorbing places for basal insulin and can spare the faster absorbing places for bolus.
religious rotating is a must, so if you feel you are developing hypertrophy, maybe start a pattern of where you injected your tresiba and follow it precisely.
hope i could somewhat help...