structural wood problem

[stcr]

Hello everybody
I'm concerned because one of the horizontal wooden beams along the base of the wall under our basement stairs is cracked completely, to the point where there is a gap because a piece of wood is missing. Should I be seriously worried and how should I go about rectifying this problem?
Thank you in advance.

 

[Static]

Post some photos if you can. Also does it support the stairs, what are the stair constructed from? Does it support the floor too? Is the basement damp, are there signs of rot on the timber? How long is it? What size is it? Are there signs of the stairs dropping? more more more info please