You should consider whether you would have been offered the job at all if you had pressed too hard for a higher salary. If you are happy to stay there, you would do well to work hard and prove your worth to the company, then next year you will have lots of evidence to negotiate a raise. I found a little video about it, which is particularly intended for British audiences, but the principles will doubtless be the same anywhere.
Salary negotiation is an important skill. Job hopping during this time can be a little difficult, but you can negotiate a better pay based on who is actually employing you.
Some employers simply do not want to negotiate a salary. They have a "fixed" budget and will not budge no matter what the case is. Some will be willing to negotiate a little and some still have no bar on the salary(well almost).
By accept do you mean that you signed the hard copy of an offer letter ? Is it possible to somehow come out of this agreement. More importantly will you be happy with the new pay and type of work ?
Some companies take it seriously to retain the right candidates. So, try talking to your manager. Before you talk to your manager, prepare for the following question. It is a skill to negotiate, but do your research and be realistic, especially in this tougher market.
Q. Why are you worth more? Reflect back on your past achievements, value-adds, contributions, etc.
If the difference in the salary is tolerable given the current market condition, etc, look for other benefits you are getting out of the company like opportunity to work on challenging and high profile projects, opportunity to learn new technologies/frameworks, opportunity take on leadership roles, etc. This will enable you to look at things as a package and prepare yourselve to make a bigger move when the market improves.
If you find yourself not being happy after evaluating the whole thing as a package, start looking for other opportunities. If you find something better and decide to move on, leave the current company amicably without burning any bridges.