you'll get used to it when you build up the muscles in your thumb. back when i raced MX i let my buddy race my blaster that raced 250a class on a dirt bike. by the end if one moto his thumb hurt so much he could not push the throttle rite on the last lap.
you need to do excercises for your thumbceps there like your biceps in your arms but in your thumbs. LOL i can run one of the 2 hour GNCC national races and my thumb don,t bother me.
JASON LISKEY
1985 atc 250r ---- finsh line axle,.fmf exhaust and rictor privateer silencer, prm grab bar.
2008 KTM 525xc quad ----- HMF exhaust, HRE chromoly stem,
86 trx 250r --- with after market chromoly frame and everything else done to it
01 400ex --- with 86 trx 250r motor
87 250x + 93 300ex both 350x powered
2 = 86 atc 350x's
86 atc 250r
83 atc 185s --- from retired guy not ridden since 87
Bandito framed 110 with 85 motor and yellow us90 fenders + tank