I tried looking up online dictionary but cannot find the meaning of 男猪脚? Its literal meaning is "I am a male pig's foot" and it makes no sense.
This is internet slang:
猪脚 refers to
主角 (they have similar pronunciation), i.e.
leading role [character]. The original meaning of
pig feet; as @NS.X. commented, as internet slang it's usually used for playfulness, sarcasm or self-mockery.
我是男猪脚 means I am the leading man (main actor).