Assuming this is direct speach to someone: the verbs in the first sentence need changing (I had heard that your hand was...); the first parenthetical simile is comparing the hand to the size of the legend of Bigfoot (and not Bigfoot's hand), I am guessing you didn't mean this; the mood of the verbs in the final clause (I would feel like I was holding); I'm not sure "baseballist" is usual (I'm not American), if not, baseball player would be better. So I would suggest as follows:
"This is just too painful ... I'd heard that your hand was as big as a bear's but I hadn't imagined it was so big! (Well, in fact, it's as huge as the legendary Bigfoot's!) So, it is really too hard for me to hold your hand - I'd feel like I was holding a baseball player's hand (the one wearing the glove)."