Why is my rat acting so hostle?

Brief：
We just got our rat last week. I was told to socialize with him everyday. I have and for the past two days he squeals and nibbles at my fingers when h.. 

We just got our rat last week. I was told to socialize with him everyday. I have and for the past two days he squeals and nibbles at my fingers when he climbs in my hand. He (or she) also jumps around when I get around his cage. I did make some changes to it by adding the topper, ya know the thing that goes on top of a 10 gallon tank so he has more room, and I moved some other things around in it. Please help. My three year old daughter also plays with him and I don't want him to eventually bite her. Should I get him a playmate or what?

Thanks to all.

If you have enough time to spend with your rat it doesn't need a friend. My oldest rat was solo for about a year and bonded to me. She doesn't care about her cagemages, its me she wants to be with. She gets depressed if a day goes by when I can't pack her around with me. There's a big difference between rats that bond to people and rats that bond to each other. Two or more rats stay more "ratlike" and prefer each other slightly over you.

Its normal for a rat to nibble and lick fingers. My girls, all rescues that started out skittish and shy, have no problems with my 3yr old handling them. Make sure she doesn't have anything that smells tasty on her hands, though. Your rat may get excited and think she's food. My boys have never been bit and the last time I was bit by a domestic rat was when I was young and... well... smelled like a treat.

Pet store rats need heavy socialization, since they've come rom a mill where they've been mass-produced. Rats need to be held and played with from the time their eyes open. Mills can't do this. Look into a breeder next time, even if its just to ask if they have a rescue that you can adopt. Even though the rescue probably came from a pet store or an unwanted litter, you can bet that they've been properly loved on. he misses his home. he wants to be released into the wild Rats need to be homed with a friend or they will get lonely and sad. Figure out the sex of your rat and get him/her a playmate of the same sex.